US officers in Anbar province watch George Bush's speech on the war in Iraq. Photograph: John Moore/Getty Images
George Bush is facing his first collision with the new Democrat-led Congress after scorn was poured on his new strategy for Iraq, set out in a televised address early this morning.

Democratic congressmen expressed almost unanimous opposition to his announcement of a deployment of an extra 21,500 US troops for Iraq on top of the 132,000 already there.

Ominously for Mr Bush, several Republican congressmen also made it clear they opposed the new deployment.

Within minutes of Mr Bush finishing the speech, the Democratic leadership issued a joint statement claiming his policy would endanger national security because it further over-extended US forces, reducing their ability to operate elsewhere.

Senator Barack Obama, one of the leading contenders for the Democratic presidential nomination, said he had not seen anything in the speech that made him think the additional troops would "make a significant dent in the sectarian violence".

Mr Obama was considering various options to ensure that Mr Bush's policy was properly examined by Congress and to ensure that "the mistake of going into Iraq was not compounded by this further mistake". He lamented the lack of any political initiative to encourage bringing Shia and Sunni Muslims together.

Congressmen will get an opportunity to press their views further later today when the US secretary of state, Condoleezza Rice, goes before a senate committee to explain the new policy, to be followed by the new defence secretary, Robert Gates.

One of the leading anti-war Democrats, senator Edward Kennedy, who has suggested that Congress could block funding for the extra troops, said: "What we really ought to be having at this time is a surge of political initiatives, rather than a surge of military initiatives." He has described Iraq as Mr Bush's Vietnam.

But senator John McCain, the frontrunner at present to win the Republican presidential nomination, insisted the war was still winnable and described the speech as "excellent". He saw it as an acceptance by Mr Bush that the previous strategy of taking ground from the insurgents and moving on had failed and he had instead opted for one in which ground would be taken and held.

Reflecting public opinion polls showing majorities opposed to the war, congressmen criticised Mr Bush free of the kind of restraints of even a few months ago when they worried about being accused of being unpatriotic.

Senator Dick Durbin, the Democratic majority whip, reminded Mr Bush that he had repeatedly claimed the US was winning the war but the speech had made clear what every American knew to be true: that the US was not winning.

Nancy Pelosi, the Democratic House speaker, said: "The American people have lost confidence in the president's policy." She confirmed a vote would be held, possibly as early as next week, on a resolution expressing lack of support for his new policy.

The vote will be held in both the House of Representatives and the Senate, where the Democrats hope to secure the support of about ten or more Republicans who are disillusioned or worried about re-election.

"This issue is, do you support the president's policy? That will be the vote," she said. "Democrats will always support the troops."

There were many Republican voices of support for the president's plan.

Senator Thad Cochran said: "I think the president deserves our support. He is starting to involve the government in Iraq and the military forces and police in Iraq in a more aggressive way. Together they have worked with our military leadership to come up with a new plan - a new plan that, if supported by Congress, has a good chance of succeeding."

But other Republicans were critical of the policy, such as senator Gordon Smith, who said US troops were being place "in the role of a traffic cop in someone else's civil war".

Mr Gordon added: "American patience is not inexhaustible, and they [the administration] have about worn it out."

Another Republican senator and possible presidential candidate, Sam Brownback, who was on a visit to Iraq, sent back a message to Washington registering his opposition.

Senator Norm Coleman also joined in, saying Mr Bush's plans would only put more US troops in the crosshairs of a sectarian insurgency. "I oppose the troop surge in Baghdad because it is not a strategy for victory," he said.